As already mentioned above, the present invention aims at providing a more accurate flow control for the forwarding of transmission information in ad hoc networks. Hereinafter, some basic functionalities of ad hoc networks will be explained with reference to FIG. 1 and FIG. 2. Further information about ad hoc networking can be found from “Wireless ad hoc networking—the art of networking without a network” by Magnus Frodigh et al. in Ericsson Review, No. 4, 2000, pages 248-263.
FIG. 1 shows a typical scenario at an airport where people can access local- and wide-area networks, for example through an WCDMA indoor base station BS and a HiperLan/2 access point AP. FIG. 1 also shows typical nodes of the ad hoc network, for example a first node MN1 formed by a personal area network of a notebook computer NC1 connected through a Bluetooth Connection to a personal digital assistant PDA1. Another node RN2 might consist of a personal area network PAN only formed by a mobile telephone MT2 and a personal digital assistant PDA2. The node MN3 is yet formed by another network of a personal digital assistant PDA3, a mobile telephone MT3 and a notebook computer NC3. However, a node like MN4 might simply be formed by a single mobile telephone MT4. Thus, in FIG. 1 user's devices can both interconnect with one another and connect the local information points—for example, to retrieve updates on flight departures, gate changes and so on. Thus, in FIG. 1, for example the node MT4 and the node MN1 might directly access information from the base station BS. For example, a user might retrieve e-mail via a HiperLan/2 interface to a notebook computer in a briefcase, but read messages and reply to them via his or her personal digital assistant PDA1, PDA3.
On the other hand, node MT4 might not only directly be connected to the mobile telephone MT2 through the base station BS but by using the node MN1 as a relaying node, i.e. the node MN1 can be used to relay traffic to the node RN2 through Bluetooth Connections which are only established “ad hoc”, i.e. not permanently. This relaying of transmission information is known as “single or multiple radio hop architecture”, i.e. transmission information from a node outside the ad hoc network might be transmitted to the end terminal node (e.g. RN2) through one (singe hop) or more (multiple hop) other ad hoc nodes.
Such a scenario is further illustrated in FIG. 2 with four interconnected nodes RN1, RN2, RN3, MN1 wherein two nodes RN1, RN3 have an internet connection via a Bluetooth LAN access point and a GPRS/UMTS phone respectively through a GPRS network GN and two routers RT. Clearly, if for example a terminal node connected to the internet or corporate IP network IN sends transmission information directed to the end terminal node MN1, the nodes RN1 and RN2 will act as relaying nodes which forward the transmission information through communication routes which are only set up on request, i.e. “ad hoc”. As shown in FIG. 2, one of the perhaps most widespread notions of the mobile ad hoc network is that the network is formed without any central administration and consists of mobile nodes that use a wireless interface to send transmission information.
It should also be noted that of course there is no need that the relaying nodes and the end terminal node are in close vicinity to each other, i.e. the ad hoc devices can also relay traffic between devices that are out of range. In addition, since the ad hoc network is based on for example a wireless mobile communication system the mobile devices move around (mobility) and thus the “ad hoc” i.e. spontaneously formed network might be spread out over large distances.
Furthermore, provided that a node is registered as an ad hoc node, the ad hoc nodes will use spontaneously assigned ad hoc addresses rather than globally fixed addresses. Thus, one of the central aspects of ad hoc networks is that these are formed spontaneously (“ad hoc”) amongst the devices which are registered as ad hoc nodes. Rather than administered by a central facility, the ad hoc nodes will establish communication connections such as a wireless Bluetooth Connection, on demand and by themselves.
Since the ad hoc nodes themselves establish connections amongst each other in an ad hoc, i.e. spontaneous way, thus increasing the coverage of existing base stations without requiring additional hardware, users need an incentive for providing their devices for the relay service. One possible incentive is that the users get a reward for the relaying service and only the end terminal node is charged for receiving the transmission information just like in conventional mobile networks. However, even if there is provided a gateway GW providing the connection to the first network IN, the gateway GW has no information whether a particular relaying node has relayed transmission information and/or whether the end node has actually received any transmission information. Thus, there is no actual accurate flow control or traffic information monitoring of the transmission information forwarding between the nodes of the ad hoc network. For example, the charging accounting for information transfer within the ad hoc network can only be based by using a mechanism in the gateway GW which accounts for the forwarded transmission information.
This problem is further illustrated with reference to FIGS. 3a, 3b which shows the typical communication system SYS considered by the present invention. The communication system SYS includes a first network IN with a least first terminal node CN (hereinafter also called the corresponding node), an ad hoc network AHN with at least a second terminal node RN1-RN4, MN and a gateway GW for forwarding transmission information TI between the first terminal node CN of said first network IN and said second terminal node RN1-RN4, MN of said ad hoc network AHN. Each node CN, RN1-RN4, MN has a corresponding transmission/reception unit TRC, TR4, TRN and also the gateway GW itself has such a transmission/reception unit TRG. The transmission/reception unit TRN is adapted to receive transmission information TI from the other terminal CN through the gateway GW either through the main route MR or through an alternative route AR which is set up as wireless connections between the individual ad hoc nodes RN1, RN2, RN3. Each of the nodes RN1-RN4, MN also has a routing means, e.g. RM4 and RMN, for achieving the relaying function as described above. The first terminal node CN has a global source identifier (global source address) SAC and each of the ad hoc nodes RN1-RN4, MN have a corresponding target address, e.g. TA4, TAN. In the transmission information memory TIS of the first terminal node CN information such as a destination address for the transmission information is stored. The transmission information TI sent out from the first terminal node CN is received by the transmission/reception unit TRG of the gateway GW and is then transmitted to the second terminal node RN1-RN4, MN. The first network IN is any kind of an operator-controlled network, for example the Internet or a mobile communication network. The gateway GW can be an access point or a base station. Not necessarily does the gateway GW belong to the ad hoc network. That is, the gateway GW is merely to form the interface between the corresponding node CN and the nodes of the ad hoc network. Thus, the ad hoc network AHN consists for example of a mobile node MN that is sending and receiving data and several candidate relaying nodes RN1-RN4. The corresponding node CN can be located anywhere outside of the ad hoc network, not necessarily in the operator-controlled network. In this scenario, the node MN could transmit data over RN2, RN1 and GW to the corresponding node CN. Furthermore, it is assumed that users of all mobile devices have a contract with the cellular network operator.
FIG. 3a also shows an accounting unit ACC adapted to determine charging information CH for the transmission of the transmission information TI to the second terminal node. For determining the charging information CH, the accounting unit ACC may determine the charging information CH on the basis of some transmission characteristics TCH determined by a transmission information characteristics determining unit TIM. These transmission characteristics TCH can also be stored in the transmission information memory TIS, as shown in FIG. 4a. If for example the determined transmission characteristics TCH comprise a data amount DAM and a transmission speed TRT, the accounting means ACC can determine a charging information CH of 7 Cent for the forwarding of transmission information of 2 MB with a transmission rate of 64 kbit/s to the target node RN4 having the target address TA. Thus, with a data set as shown in FIG. 4a in the transmission information memory TIS, it is easy for the accounting unit ACC to provide some kind of accounting for the downlink (from corresponding node CN to the target ad hoc node).
For uplink transmission information (for example from the ad hoc mobile node MN to the corresponding node CN through the gateway GW), it is obvious that the gateway GW only receives and charges/rewards transmission information which did not get lost. Thus, in the uplink direction the gateway GW can always perform some kind of accurate accounting.
However, problems arise regarding the accurate flow control or accurate accounting regarding the downlink transmission information. Actually, users should only be charged and rewarded for transmission information that they actually have transmitted and should only be charged for transmission information which they actually have sent or received. However, since the gateway GW has no information whatsoever what happens to the transmission information TI after it has been sent out by the transmission/reception unit TRG of the gateway GW, the accounting unit ACC can only make a guess whether or not the transmission information has actually reached the desired ad hoc and terminal node, e.g. MN. This is generally true, not only for the specific example of having to provide an accurate accounting. Namely, the gateway GW can generally transmit transmission information but it has no actual control over it because no further information about the possible arrival or non-arrival of the transmission information is available. Therefore, the gateway GW can not generally perform any other accurate control (flow control) of the transmitted transmission information.
For example, as shown in FIG. 3b, if there is a cut-off of a wireless link along the main route MR between two relaying nodes RN1, RN2, then the gateway GW has no possibility to know whether or not the transmission information TI has actually arrived at the second terminal node MN. Thus, the gateway GW, i.e. its transmission information memory TIS can only store information about all transmission information which it has sent to the second terminal node MN in order to perform proper charging and rewarding. However, the entire accounting is intrinsically based on the assumption that the entries in the transmission information memory TIS reliably relate to a transmission information which has actually reached the second terminal node. If not, as shown in FIG. 3b, the mobile end node MN would be charged for transmission information which has not been successfully delivered.
On the other hand, the user of the second end terminal node MN might simply contest that it has received any transmission information, even if it has arrived, in order not to be charged by the gateway GW. In such a scenario, the gateway GW has no means to verify and to demonstrate to the second terminal node MN that the transmission information TI has actually arrived and that the charging information CH is accurate. Since the gateway GW has no evidence that the transmission information TI has actually arrived at the second terminal node MN, despite the fact that the transmission information TI has arrived, a misbehaving second terminal node MN might achieve that it does not have to pay for the transmission information which it actually has received.
It should be noted that the above described problem of accurate accounting is only one sub-problem of the general problem that the gateway GW cannot provide an accurate flow control of the packets. For example, also other flow control mechanisms in the gateway GW might require accurate knowledge about the fact whether or not the transmission information TI has actually arrived at the desired target terminal node MN. For example, another flow control for the transmission information TI could involve the increase or decrease of transmission rate or the complete stoppage of transmitting transmission information TI if it was known that one of the wireless links on the main route MR or the alternative route AR has failed.
Another example of insufficient flow control is the occurrence of a congestion on the main route MR or alternative route AR which calls for a reduction of transmission rate. However, in conventional ad hoc networks the gateway GW has no possibility of detecting any reasons of loss of transmission information, such as noise, congestion or misbehavior of users/devices.
In Bakre A.V. et al.: “Implementation and Performance Evaluation of Indirect TCP”, IEEE Transactions on Computers, IEEE Inc., New York, Vol. 46, No. 3, 1 March 1997, pages 260-278, XP000685987, ISSN: 0018-9340, there is described an implementation and performance evaluation of indirect TCP. In more detail, there is presented the implementation and performance of I-TCP, which is an indirect transport layer protocol for mobile wireless environment. Throughout comparison with regular TCP shows that I-TCP performs significantly better in a wide range of conditions related to wireless losses and host mobility. There is also described the implementation and performance of I-TCP handoffs.
Further, in US 2002/036991 A1 (Inoue Atsushi), there is described a communication system using access control for mobile terminals with respect to a local network. In a communication system, even when a mobile terminal device belonging to some mobile carrier does not have a right or a qualification for accessing the fixed communication network via the local network/gateway that is given in advance, this mobile terminal device is enabled to access the fixed communication network via the local network/gateway. This is achieved by carrying out a procedure for paying the fee from the user of the mobile terminal device to the fixed communication network provided or a procedure for monitoring the mobile terminal device.
Further in Patent Abstract of Japan, Vol. 2002, No. 11, 6 November 2002 & JP 2002 209028 (Mitsubishi Electric Corp.), 26 Jul. 2002, there is described an adhoc network where a start point terminal, relay terminals, and an end point terminal are used to dynamically configure a communication network. The relay terminal records a fact of communication path setting execution together with identifiers of the start point terminal and the end point terminal and the recording is used for a basis of charging information.
Further, in EP-A-0 903 905 Tokyo Shihaura Electric Co.), there is described a scheme for reliable communications via radio and wire networks, using transport layer connection. Here, a gateway device determines whether or not to carry out a set-up of a connection in divided forms according to an information content of a packet that contains a transport layer protocol data unit requesting a set-up of the transport layer connection between the radio terminal of the radio network and the wire terminal of the wire network.
Further, in U.S. 2002/045424 A1 (Lee Hee Dong), there is described a Bluetooth private network and communication method thereof. The Bluetooth private network comprises Bluetooth access points, each functioning as a base station in each of Bluetooth piconets, a gateway for functioning as an interface between a public network and the Bluetooth private network, sending a beacon signal to each of the Bluetooth devices in local Bluetooth networks to locate the Bluetooth device and a router for functioning as an interface between each of the Bluetooth access points.